Italian geneticists managed to establish the boundaries and structures of their own community only after the Second World War, when they promoted, in the space of a few years, a series of initiatives culminating in the Ninth International Congress of Genetics (Bellagio 1953). This essay traces the ways in which, from the beginning of the century, the revolutionary and swift development of the discipline found its context and interested audience in Italy. In contrast to our standard picture, there was no shortage of naturalists to dedicate themselves enthusiastically to genetics, even launching a campaign in the 30's for its "political" recognition. But cultural trends after the First World War, and especially the directives of the Fascist regime, tended to favour scientific practical and economic values and keep the theoretical and interpretative nature of their work to a minimum. This was ultimately futile, given the indifference with which the centres of power responded. It was the reason, too, for their extremely weak, or almost non-existent participation in the preparations for the evolutionary synthesis in which European and American scientists were involved, which changed appreciably the character and methods of biology.